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The journal of high energy physics, 2015-09, Vol.2015 (9), p.1-26, Article 16
Ort / Verlag
Berlin/Heidelberg: Springer Berlin Heidelberg
Erscheinungsjahr
2015
Link zum Volltext
Quelle
EZB Free E-Journals
Beschreibungen/Notizen
A
bstract
The combination of data from long-baseline and reactor oscillation experiments leads to a preference of the leptonic CP phase
δ
CP
in the range between π and 2π. We study the statistical significance of this hint by performing a Monte Carlo simulation of the relevant data. We find that the distribution of the standard test statistic used to derive confidence intervals for
δ
CP
is highly non-Gaussian and depends on the unknown true values of
θ
23
and the neutrino mass ordering. Values of
δ
CP
around π/2 are disfavored at between 2σ and 3σ, depending on the unknown true values of
θ
23
and the mass ordering. Typically the standard
χ
2
approximation leads to over-coverage of the confidence intervals for
δ
CP
. For the 2-dimensional confidence region in the (
δ
CP
,
θ
23
) plane the usual
χ
2
approximation is better justified. The 2-dimensional region does not include the value
δ
CP
= π/2 up to the 86.3% (89.2%) CL assuming a true normal (inverted) mass ordering. Furthermore, we study the sensitivity to
δ
CP
and
θ
23
of an increased exposure of the T2K experiment, roughly a factor 12 larger than the current exposure and including also anti-neutrino data. Also in this case deviations from Gaussianity may be significant, especially if the mass ordering is unknown.